The invention relates to a protection circuit for integrated circuits, in particular, for integrated circuits for motor vehicles.
In recent years, electronics have become increasingly more important in automotive technology. As a result of this development, integrated circuits are being used to an ever increasing extent in motor vehicle technology. These integrated circuits are subject to interference signals which, at least in this day and age, are still not avoidable in automotive technology. The interference signals occur in the form of voltage pulses which are characterized by a so-called V/T ratio. In this case, V represents the voltage which the interference pulse reaches, while T stands for the time required by the interference pulse to get from a certain voltage value on its rising slope to the same voltage value on the falling slope.
FIG. 1 shows an example of the voltage/time path of an interference pulse in motor vehicles. On the abscissa of the coordinate system in FIG. 1 is written the time t, and on the ordinate the voltage U. U.sub.s represents the maximum voltage reached by the interference pulse. T stands for the time required by the interference pulse to get from a certain voltage value on its rising slope to the same voltage value on the falling slope. In FIG. 1, that certain voltage value is 10 percent of U.sub.s.
According to new requirements, for example, integrated circuits for the automotive industry must be immune to interference pulses with U.sub.s =+100 V/300 ms or U.sub.s =80 V/400 ms, respectively. Interference pulses of this kind do, however, lead to unacceptably high power dissipation in the integrated circuit and to destruction with the known protection circuit technology.